The exemplary embodiments described herein relate generally to semiconductor devices and methods of forming such devices and, more specifically, to semiconductor devices comprising magnetoresistive random-access memory (MRAM) structures and methods for the formation thereof.
Magnetoresistive random-access memory (MRAM) is a non-volatile random access memory technology in which data is stored using magnetic storage elements. The elements are formed as a magnetic tunnel junction (MTJ), which is a cell formed by the arrangement of two ferromagnetic layers, each of which can hold a magnetization, separated by a thin insulating layer that forms a tunnel barrier. One of the ferromagnetic layers may be a permanent magnet of a particular polarity, whereas the magnetization of the other layer may be a writable layer that is matched to that of an external field to store data. Generally, for two layers having the same magnetization alignment (for example, arranged in parallel), the resistance state is low and is assigned a value of “1.” If the two layers have magnetizations that are in anti-parallel alignment, the resistance state will be considered to be high and will be assigned a value of “0.” A plurality of such cells arranged in grid form forms a memory device.
Methodologies for the formation of MRAM structures in the prior art involve the use of an etching process to form self-aligning bottom electrodes which are used to connect an MRAM structure to an access transistor. MRAM formation processes are carried out in which copper is deposited in an MRAM area of a substrate, the copper is then recessed, the recessed areas are filled with tantalum nitride (TaN) or titanium nitride (TiN), and the MRAM area is subsequently subjected to a chemical mechanical polish (CMP) to planarize the surface. However, during planarization, the TaN or TiN often delaminates from the copper. Additionally, during physical ion mill etching processes in which tapered profiles of the magnetic tunnel junction (MTJ) pillars are corrected, shorting across the magnetic tunnel junction and damage to dielectric material around the MTJ pillars may occur.